To be more clear (get it?

) Jock Clear is not officially on Leclerc's team anymore. Maybe he still acts as a personal coach for Leclerc since they're close but he isn't in Leclerc's garage technically. He is the head of the FDA (Ferrari Driver Academy) and that's his primary role in Ferrari.
As woocasz says, Leclerc's current performance engineer is Johannes Hatz, he took over the position when Bozzi was promoted to race engineer.
Diella seems to be the new engineer for Hamilton, if you look up his CV he has been with Ferrari for a few months and he previously worked at Mercedes.